Oligodendrocytes obtained from rat brain 0-2 A progenitor cells and differentiated in culture take up -alanine and synthesize carnosine (-Ala-His). The present study was designed to determine whether carnosine and -alanine are released from such cultures in response to some stimuli. An evoked release of these substances was not observed when the cells were incubated with 1mM glutamate or 0.3 mM kainate. Addition of 0.1 mM cyclothiazide (CTZ) to the corresponding stimulus was accompanied by a distinct peak of release consisting of both carnosine and -alanine. The efflux was blocked completely in the case of kainate and to 80% in the case of glutamate when 50 µM 6,7-dinitroquinoxaline-2,3 (1H,4H)-dion (DNQX) was added to the cells at the same time as the receptor agonist. An increase of the efflux was observed in the presence of Zn 2ϩ . This effect was concentration-dependent. Total substitution of NaCl in the efflux medium by LiCl caused only a partial reduction of the release. GABA or 55 mM KCl showed only negligible effect. A large release of carnosine and -alanine was observed when oligodendrocyte cultures were treated with Ca 2ϩ ionophore A 23187. These results suggest that oligodendrocytes exhibit a glutamate receptor-mediated release of carnosine and -alanine. The release is dependent on elevated intracellular Ca 2ϩ concentration.